Spring



G. MUFFLY July 20, 1937.

SPRING Filed April 14, 1936 Gary fl/Wy,

Patented July 20, 1937 p UNITED STATES PATENT orrlca SPRING Gary Mumy, Oakmont, Pa, aaaignor to Gulf Research & Development Company, Pittsburgh, Pa, a corporation of Delaware Application April 14, 1936, Serial No. 74,356

Claims. (CL 267-1) This invention relates to springs; and it com- Referring to the drawing, Fig. 1 shows the prises a coiled spring comprising a thin band invention as embodied in a gravimeter. There is wound into spiral shape, the band having spaced provided a helical spring composed of a thin band laterally-flexible portions along its length with or ribbon 20 of metal or other resilient material,

5 stiff reinforcing portions between the flexible provided along its length with spaced slots 2| 5 portions, and having continuous edges, so that the the major axes of which are parallel to the axis spring gives a high angular deflection upon of the helix. The spring is attached at its upper axial stress; all as more fully hereinafter set end to a fixed support 22 as by rivets 23. At forth and as claimed. the lower end is attached a post 24 carrying One object of the invention is to provide a an annular mass 25. The lower end of the 10 helical spring which affords a high angular despring and weight assume a certain definite poflection or twist, under loading in the direction sition corresponding to the force 01' gravity at of the axis of the helix. the place where the gravimeter is set up. Upon Another object is to provide a helical spring moving the instrument to a location of greater made of a'colled ribbon, the ribbon being modior less gravity, the weight of annulus 25 changes is tied so as to increase its lateral flexibility while to a minute degree. This stresses the spring, preserving its axial rigidity. which unwinds through a definite angle in the Another object is to provide a spring suitable direction oi the arrow upon increase in gravity, for use in apparatus measuring very small force and winds in the reverse direction upon decrease changes, and adapted to give a high angular dein gravity. The deflection is measured by suit- 20 ilection when subjected to such force changes. able indicating means, not shown. Angular de- There has recently been developed a graviflection is aiforded by a simple helical spring meter, that is a device for measuring the force arranged similarly; but the deflection of my of gravity on the earths surface, which comspring is much greater. This is because the torprises a freely hanging mass suspended from sional flexibility is enhanced while the vertical 25 a fixed support by means 01' a ribbon helix spring, rigidity is but little changed. When it is conthat is to say a coil spring made by winding up sidered that the changes to be measured in a thin flat ribbon or tape into a helix. Upon gravimetry are often only 1 part in 10,000,000 or setting up the apparatus in a given locality the so, the advantages of my spring, which gives an mass and the spring remain in a certain definite angular deflection several times that of a flat 30 flxed position, determined by the force of gravity ribbon spring, are manifest. at the spot. Upon moving the apparatus to a In all cases the ribbon is much thinner than it locality in which the force 01 gravity is different, is wide, so as to get as high angular deflection the weight of the mass changes. This stresses sensitivity as possible. The thickness usually or stretches the spring'and causes an angular ranges from 0 1/600 of t e W dth. 5 deflection of the unfixed end of the spring; the Fig. 2 shows a portion (about half a turn) of helical spring having the remarkable property of the spring of Fig. l as laid out flat; that is, the twisting substantially under axial loading, withflgure shows a portion of the ribbon from which out much elongation. the coil spring is made. It will be noted that 40 The present invention relates to an improved the slots are parallel to the vertical axis, and 4 type of spring which is particularly well adapted thus are not at right angles to the axis of the for use in such type of gravimeter, but which ribbon. This arrangement is most advantageous, also has wide applicability in all other cases as the torsional flexibility and the vertical rigidwhere it is desired to measure and indicate force ity are both maximum. However, the slots need changes as an angular deflection. not be strictly parallel to the helix axis; they 45 The stated objects are achieved by providing a can be disposed at right angles to the ribbon helical spring made up of a coiled band, the band axis, if desired, without much loss in efllciency. being modified to enhance its lateral flexibility. Fig. 3 shows a ribbon provided with slots so Examples of specific embodiments of my inbroadened as to form squares (approximately) vention are shown in the accompanying drawing, as indicated at 28. This arrangement gives very 50 in which high torsional flexibility with not much loss Fig. 1 shows a slotted ribbon helix spring emin vertical rigidity. bodied in a gravimeter, and Fig. 4 shows a modification having hour-glass Figs. 2 to 13 show springs modified in various shaped slots 29. This type has properties interways to enhance the torsional flexibility. mediate those of Figs. 2 and 3. Fig. 6 shows 55 the arrangement of Fig. 4 carried a little further, so that a double row of triangular slots 30 is formed.

Fig. 5 shows a modification of Fig. 2 in which the slots are replaced by spaced series of holes 3|. This modification has slightly less torsional flexibility and slightly greater vertical rigidity than the Fig. 2 spring.

Fig. 7 shows a modification wherein the slots are shaped as triangles 32, so spaced as to leave strut-like portions 33. This arrangement has almost as high torsional flexibility as Fig. 3 and a substantially higher vertical rigidity.

Figs. 8-11 show modifications wherein enhanced torsional flexibility is secured by lessening the thickness of the ribbon at intervals along its length by provision of grooves rather than by making holes clear through as in Figs. 1-7. In Figs. 53-11 the thickness of the ribbon is exaggerated for the sake of clarity of showing. In Fig. 8 the ribbon is provided with parallel rectangular grooves 34, depressed below the surface leaving thicker, post-like portions 35. The spring of Fig. 9 is similar, but has rounded post-like portions 36, with intermediate depressions 3'! and thus is well adapted to be made by rolling a flat strip. Fig. 10 shows a modification particularly well adapted to be made by rolling operations, having concave grooves 38 as shown. The device of Fig. 11 is similar to that of Fig. 8, but has grooves 34 on only one side.

In Figs. 8 l1 the depth of the grooves is determined in accordance with the average stress to which the spring is to be subjected. If the spring is required to resist a heavy force, the grooves are made shallow. If the spring is to be but lightly loaded, the grooves can be deepened with consequent gain in angular sensitivity.

Fig. 12 shows a modification which is very easily made. The ribbon is provided with corrugations 39 which act somewhat like hinges, making the ribbon considerably more flexible in the lateral direction without diminishing the vertical rigidity to anything like the same extent.

In some cases, particularly in large scale apparatus, it is convenient to make up the springs out of separate elements rather than to form them in one piece. Fig. 13 shows one such spring, comprising two spaced bands 40 having spaced struts 4i rigidly attached to each band as by rivets 42, providing an arrangement analogous to that of Fig. 3.

My springs can be made in various ways. Those in which material is removed from a plain ribbon can be made by cutting, grinding, punching, acid etching, sand blasting or other known mechanical methods. Such forms as that of Fig. 13 can be constructed by welding, soldering, riveting, etc.

While the spring shown in Fig. l is a true helix, that is of cylindrical form with coils of constant pitch, the advantages of the invention are secured when the spring is made to have varying pitch, or departs from cylindrical form, or takes the form of a plane spiral rather than a three-dimensional spiral.

The spring can be of any length required and can of course be mounted horizontally or otherwise as required in the particular apparatus with which it is used.

The springs are ordinarily made of steel of characteristics similar to those of clock spring steel.

What I claim is:-

l. In measuring apparatus, a coil spring in the form of a helically wound thin ribbon, the ribbon having spaced laterally-flexible portions along its length with stiff reinforcing portions between the flexible portions, whereby to secure high angular deflection upon axial stress, the edges of the ribbon being continuous whereby to provide rigidity along the direction of the helix axis.

2. In measuring apparatus. a coil spring adapted to give a high angular deflection upon axial loading, comprising a band wound in helical shape with the coils free from frictional contact with each other, the band having grooves spaced along it in the direction of its length and providing portions of high lateral flexibility.

3. In measuring apparatus, a coil spring adapted to give a high angular deflection upon axial loading, comprising a band wound in helical shape with the coils free from frictional contact with each other, the band having a plurality of spaced grooves extending substantially transversely of the band and providing portions of high lateral flexibility.

4. A coil spring for measuring instruments adapted to give a high angular deflection upon axial loading, comprising a thin wound-up band having a plurality of transverse slots therein spaced along the band's length and terminating short of the edges of the band and arranged to increase the lateral flexibility.

5. In measuring apparatus having means for suspending a helical coil spring and means for producing an axial stress on the spring. an improved coil spring in the form of a ribbon wound in a helix in such manner that the coils of the helix are free from frictional contact with each other, the ribbon having spaced laterally-flexible portions along its length with stiff reinforcing portions between the flexible portions, whereby to secure high angular deflection upon application of said axial stress, the edges of the ribbon being continuous so as to pr ovide rigidity along the direction of the helix axis.

GARY MUFFLY. 

